Less than a decade old, biological interaction analysis (BIA), offers unique approaches to the study of kinetics, stability and specificity of interactions among biological macromolecules and their ligands. Based on the phenomenon of surface plasmon resonance (SPR), BIA does not require radioactive or chromophore labels and is suitable for analysis of proteins, peptides, nucleic acids, carbohydrates, lipids and various low molecular weight molecules. BIA is done in real time, allowing evaluation of the kinetics of the interactions ion many cases. We propose acquisition of a BIA instrument for use by a community of biochemists, molecular biologists, and biophysical chemists at Penn State. The instrument will be a component of the Macromolecular Interactions Facility (MIF), which has just acquired a Beckman XL-analytical ultracentrifuge. Faculty in several Colleges and Departments will utilize the MIF instrumentation. Intellectual interactions among these scientists cross traditional departmental lines, as exemplified by two groups, (I) the Center for Biomolecular Structure/Function and (ii) the Chemical Biology option in the integrative Biosciences degree program, in which most of the involved faculty participate. Eight coinvestigators will study systems that vary from prokaryotes to man in their origin and involve protein- protein, Protein-DNA, protein-RNA, and protein-small moleule interactions. Specific areas of investigation include: protein-protein interactions in assembly of the bacteriophage T4 replication complex; effect of post- translational modification on interactions of proteins that are critical in insulin control of translation; biophysical properties of proteins that bind heme; folding and multimerization of proteins; development of novel methods for study of small molecule-protein interactions by SPR; interactions of the proteins and DNA that form the eukaryotic basal transcription complex; association of histones, a repressor and structural proteins in formation of repressive chromatin domains; and interactions of three regulatory proteins with each other and with DNA in the HIV-1 long terminal repeat promoter. From protein folding to AIDS, the proposed instrumentation will facilitate interactions among a diverse group of scientists at Penn State.